At least 13 people, including one gunman, were killed in a shooting rampage Monday morning that shocked American service men and women that even at home they face imminent threats and violence. 

Police were looking for other potential suspects at the naval yard in Washington D.C., but have "nothing" to indicate additional shooters amid conflicting reports, police official said. The gunman that was killed was identified as Aaron Alexis, 34, through his fingerprints.

According to the Navy, Alexis enlisted as a full-time reservist in May 2007 and left the service in January 2011. Serving as an aviation electrician, he was assigned to Fleet Logistics Support Squadron 46, in Fort Worth, from Feb. 2008 to the end of his service. He had been awarded the National Defense Service Medal and the Global War on Terrorism Service Medal.

As the search for the two additional shooters continued, officials said one of the two gunmen at large was a white man wearing a khaki Navy uniform and carrying a handgun. The other was a black man, about 50 years old, who was believed to be carrying a "long gun," police officials said, according to New York Times.

"The white male being sought in connection to the #NavyYardShooting has been identified and is NOT a suspect," tweeted the city's deputy mayor for public safety Paul A. Quander Jr. just moments after police chief Lanier's afternoon briefing.

A former senior federal law enforcement official told New York Times that the two potential suspects had been spotted 20 minutes after the shooting, and that witnesses saw them running with weapons, not firing them. "If you are in a military building and there is some type of attack, men wearing military uniforms will undoubtedly be seen running with guns in the aftermath, and that there would be a lot of confusion," the official said.

Three victims who survived the shooting were all expected to recover, doctors at MedStar Washington Hospital Center said. One police officer was shot multiple times to his legs. A woman was shot in the shoulder, and another, who was shot in the head and hand, did not require surgery because the bullet did not penetrate her skull, hospital officials said, according to the New York Times.